Without checking I can't be 100% certain but it is possible that the scene which you described actually 'did' feature the entire British Army. The BBC placed a memo to army HQ and mid-week (when they army are usually less busy) the entire army showed up to guest alongside 'Dr. Whom'.
The dinosaur episode was a true great in the history vaults George; a good call it must be stressed. However, although 'Worzel Cribbage' was a classic 'Dr. Whom', my affinity is with Thomas Baking Cake, an absolute masterful man full of gravitas in everything he does. There were rumors of a Hollywood 'Dr. Who'm (thinking about it, did this come out?) but surely they could not or could not have hoped to capture the essence of the original series with its (as you remarked) slightly below par scenery obtained from a boot sale and the cafeteria.
I did enjoy 'Peter Rogers within the 21st Centurion' but seeing it recently for a fleeting moment it was utter tripe. Whereas 'D. Whom' stands the testaments of time management. The original 'Starvation Trek' was truly an original experience and I can still remember to this day when I guest starred on the 'Tribbles' episode as one of the Tribbles, Nigel Tribbly. You may recall the scene in which one of the better, more handsome Triffids leapt down Captain Tiberius James Cake's tight jumper searching for droppings after he opened a cupboard, presumably searching for Spot?
'The Triffids' (nice link) was a good show, with again the use of inferior plastics - and also the props. and monsters weren't much better. 'V' The Snake Attack was great first time 'round and featured some of the members of 'The A-List Team' also an early Raymond Englund pre-'A Nightmare Scenario on Almond Street'. He played the goodie in 'V' didn't he the little squealer.
This is the real thing though, weren't the plaggy monsters more scarier than the comedic CG efforts of the modern filming era?
